Git clone cache

[ipsi]

• [x] Ready for review
• [x] Follows CONTRIBUTING rules

What does this PR do?

Add ability for Client to perform a git clone as a caching mechanism

To work around rate-limit issues, it is now possible for the Client to perform a Git Clone, and to look up certain requests in that cloned version of the repository. The clone is triggered by a request for a list of files (to prevent cloning the entire repository if we only need a single file), and has a default lifetime of 5 minutes.

This adds more complexity to the deployment of the client, as it is necessary to do a full clone of the repo, and potentially multiple clones of the repo (if, for example, multiple different revisions are needed) and this requires a potentially large amount of storage.

This feature is disabled by default, and is only available for GitHub and GitHub Enterprise when enabled.

Where should the reviewer start?

How should this be manually tested?

Any background context you want to provide?

Screenshots

Additional questions